User blog comment:MegaGyarados/PokéPolls - Episode 2 - Hardest Gym Leader - Results!/@comment-32358261-20180220022110/@comment-32358261-20180220035902

What if you nominate iconic hard battles like Whitney and Cynthia. Red from gsc was apparently hard too. Ultra necrozma is known as the ultimate nuzlocke killer.

So first do nominations and the top 5 most nominated becomes the list. Or from each category. Champions, rivals, gym leaders, evil team, legendary. There could be more categories. Or do a specific category at a time